This invention relates to methods and apparatus for operating spark-ignited reciprocating-piston internal combustion engines in which the flow of intake and exhaust gases is controlled by periodically actuated intake and exhaust valves and exhaust gases are recirculated.
German Offenlegungsschrift No. 2 125 368 discloses an arrangement for internal exhaust gas recirculation in an internal combustion engine in which periodically actuated intake and exhaust valves are controlled in such a way that, during the opening of the intake valve, the exhaust valve is opened briefly by an additional lobe on an exhaust valve control cam and, as a result, exhaust gas is recirculated from an exhaust duct into the combustion chamber by the downward motion of the reciprocating piston during the overlap phase between the intake valve and the exhaust valve. At idling speeds, this actuation of the exhaust valve during the intake stroke ceases, this being accomplished by operation of hydraulic regulating tappets. This appears to provide a possible improvement in the smoothness of operation of the internal combustion engine resulting from increased turbulence in the fresh-gas charge, i.e., by the homogenization of the fresh gas supplied as a result of the exhaust gas introduction. There is no indication in this disclosure as to how the gases are guided in the internal combustion engine.
European published application No. 0 063 305 A1 discloses a spark-ignited reciprocating-piston internal combustion engine having an adjustable-stroke intake valve which is recessed relative to the combustion chamber in order to burn leaner mixtures. To obtain reliable ignition of the lean mixture, a chamfer is arranged in the form of a guide duct provided on one side in the region of the transition from the inlet cross-section of the intake duct to the combustion chamber, and this guide duct guides the induced mixture toward the spark plug.